1. Introduction
Matuyama-Brunhes magnetic reversal occured approximately 781 kyr ago (Lourens et al., 2004). Studies in recent years (Channel et al., 2010; Giaccio et al., 2013; Jin and Liu, 2011; Kitaba et al., 2013; Liu et al., 2016; Okada et al., 2017; Pares et al., 2016; Sagnotti et al., 2010, 2014; Suganuma et al., 2010; Valet et al., 2014; Bella et al., 2019) have shown that this event is well recorded by respective sediments that had sufficient sedimentation rate and could be analyzed, in detail, by paleomagnetism.
Sediments acquire remanent magnetization during their deposition. The alignment of ferromagnetic grains occurs in the direction of the earth’s magnetic field and acquisition of primary magnetization due to this sedimentation process is called depositional or detrital remanent magnetization (DRM) (Gubbins and Herrero, 2017). Remanent magnetization protected by energy barriers can last over geologic time scales. Nevertheless, due to thermal and/or chemical processes such as reheating, oxidation and formation of iron hydroxides during time, barriers may be overcome, the magnetic domains change their arrangement and rocks can acquire secondary magnetizations. The new secondary magnetization has an orientation in the direction of the Earth’s field. Then rocks can acquire a viscous magnetization (VRM) long time after their formation due to an exposure to geomagnetic field. VRM contrinutes to a noise in paleomagnetic data (Lanza and Meloni, 2005; Butler, 1997).
Lock-in-depth affects the nature of the paleomagnetic recording process in sediments. It is defined as the depth at which the remanent magnetization is stabilized. Lithology, grain-size distribution of the sediment matrix, sedimentation rate and bioturbation, all have influence on the position of the lock-in-depth in the sediments (Sagnotti et al., 2005; Bleil and von Dobeneck, 1999). When assuming the steady sedimentation rate, the result of lock-in-depth stabilization is younger magnetization than the sediment itself by an amount of time required to accumulate sediment layer of thickness that equal to the lock-in-depth. For example, if the sediment has accumulation speed 1 mm per 1000 years, and lock-in-depth is 10 mm, the magnetization age is 10 000 years younger than the sediment itself (Sagnotti et al., 2005).
Kadlec et al. (2005, 2014) reported that the Central European cave (local name “Za Hajovnou”), in the Moravia region of the Czech Republic, has a potential record of Matuyama-Brunhes transition. Here we obtained a new paleomagnetic dataset from three vertical sediment profiles found in this cave.